For centuries, arsenic was the go-to poison in the high circles of Europe, either to knock out political foes or to simply eliminate people on the dastardly way to a high state position; it was odourless, tasteless, and until 1830 – when chemist James Marsh developed a test – impossible to detect. Thankfully, we’re dealing with much less intentional arsenic poisoning today, but unfortunately, we’re dealing with much more accidental poisoning. Recently, scientists discovered a population that developed natural immunity to arsenic, high in the Andes.

Image: Wikimedia/Guigue

The dominant basis of arsenic poisoning is from ground water that naturally contains high concentrations of arsenic. A 2007 study found that over 137 million people in more than 70 countries are probably affected by arsenic poisoning from drinking water. At high doses, the metal can cause vomiting, convulsions and eventually results in coma  and can even be fatal. Low exposures over a longer period of time have been linked to liver and cardiovascular diseases, diabetes, skin lesions and cancer.

There is no cure or treatment for chronic exposure to arsenic, so any clue would be much welcome in the fight against this issue which plagues so many people world wide. Researchers from Sweden say they have identified a population in Argentina that has evolved a genetic mutation, which enables them to naturally inactivate arsenic toxicity, at least to some extent..

“They metabolise arsenic faster and to a less toxic form compared to an American or Westerner,” the study’s lead author, Karin Broberg, a geneticist at Karolinska Institutet, a medical university in Sweden, told NPR. “This is the first evidence of human adaptation to a toxic chemical.”

Archaeologists had previously found 7,000 year old mummies with traces of arsenic in their hair, so this led scientists to believe that the population had been living in a contaminated area for very many generations, something which seems to have gradually created a specific adaptation. The research team performed a genome wide survey on a group of 124 Andean women, and analyzed their urine to see how well they metabolize arsenic.

They found a significant difference in the way they are able to metabolize arsenic; basically, they are not affected by chronic exposure to it (or are less affected). The exact date at which this evolutionary trigger took place remains unknown, but this phenomenon might new insights regarding not only how we can fight arsenic poisoning – but how resistance to such substances occurs genetically.

Journal Reference: Carina M Schlebusch, Lucie M Gattepaille, Karin Engström, Marie Vahter, Mattias Jakobsson and Karin Broberg. Human Adaptation to Arsenic-Rich Environments. doi: 10.1093/molbev/msv046